1. Field of the Invention
The present invention relates to a coin discriminating apparatus capable of determining with high accuracy the denomination and authenticity of a coin by a simple process based on information on surface displacement irregularities of a stamp (strike) pattern on a coin surface. More particularly, the invention relates to a coin discriminating apparatus wherein a histogram of surface displacement irregularities information indicative of a stamp pattern on a surface of a coin is created as feature information and is collated with a histogram obtained beforehand with respect to a true coin (one of coins to be handled), thereby to identify the authenticity and denomination of the coin with high accuracy based on the stamp pattern on the coin surface.
2. Description of the Related Art
In vending machines, automatic teller machines (ATMs), etc., a coin discriminating apparatus is incorporated to determine the denomination and authenticity of coins, as a process preliminary to the calculation of the sum of inserted coins. This type of coin discriminating apparatus is generally designed to measure the outer diameter, thickness and weight of a coin and compare the measured values with previously obtained outer diameter, thickness and weight of a true coin (one of coins of different denominations to be handled) to determine the denomination of the coin, and nonauthentic coins are rejected. Among a diversity of coins, however, there are coins, for example, coins used in foreign countries, that should not be accepted but yet have features (outer diameter, thickness, weight) resembling those of true coins to be accepted, and such coins can be erroneously judged to be authentic.
Attempts have therefore been made to acquire, in the form of an image, information on surface displacement irregularities of a stamp pattern on a coin surface and recognize features of the image, thereby to identify the denomination of the coin. However, in cases where the features (pattern) of an image showing the stamp pattern on a surface of a coin to be discriminated are compared with those (pattern) of an image showing the stamp pattern of a true coin, it is necessary that a matching process be performed following the rotation of the image for comparison, or that an extra process such as Fourier transform be performed as needed. Thus, a complicated process is required for the discrimination of coins and the process consumes much time.